1. Field of the Invention
This invention generally relates to the field of power supplies for electronic equipment. More specifically, this invention relates to an apparatus for margining the input voltage command to a voltage regulator.
2. Description of the Related Art
Some voltage regulators, particularly those packaged as a voltage regulator module (VRM), are voltage ID (VID) programmable, which means that the microprocessor can program the voltage regulator to provide the correct voltage during power-up. Proper voltage must be supplied to the processor for reliable operation. Voltage may be supplied by a regulator on the motherboard, or by a VRM (Voltage Regulator Module) installed on the motherboard.
Computer system manufacturers typically assemble a variety of components such as microprocessors, input/output devices, storage devices, and video and audio devices in their products. Many of the components utilize solid state logic circuits that manufacturers test at nominal operating voltages, as well as voltages at margins of tolerance about the nominal values. These tests are conducted to determine the susceptibility of the system to fluctuations in supply voltage.
Currently, supply voltages are modified by manually adjusting the output of the power supply. This method has the drawbacks of being time consuming and costly. It is also prone to errors such as incorrectly adjusting the voltage. It is therefore desirable to supply an apparatus capable of adjusting the output of the power supply electronically and automatically during test mode. This apparatus may also be utilized to adjust the power supply to the nominal voltage value when supply voltage fluctuations occur.
The present invention provides a system and method for biasing supply voltage requirements that are input to a voltage regulator to facilitate testing a computer system with supply voltages above and below specified operating values. The present invention may also be used to compensate a voltage regulator that is not outputting the supply voltage required by the computer system.
The system includes a processor voltage signal indicative of supply voltage required by one or more components in a computer system during operation, at least one other voltage signal indicative of supply voltage for a computer system, and a selection control signal for selecting between the processor voltage signal and the at least one other voltage signal. The processor voltage signal, the at least one other voltage signal, and the selection control signal, are input to a multiplexer. The multiplexer outputs a voltage identification signal to the voltage regulator based on the processor voltage signal, the at least one other voltage signal, and the selection control signal.
In one embodiment, one of the at least one other voltage signals is a margin voltage signal indicative of supply voltage input to the computer system during test conditions.
In another embodiment, the supply voltage being provided by the voltage regulator is not within tolerance of the supply voltage required by the computer system. In this situation, one of the at least one other voltage signals is a margin voltage signal that includes a bias that is input to the voltage regulator to compensate the supply voltage to the voltage required by the computer system. Program logic may be included in the system to determine the bias to add to the margin voltage signal.
One feature of the present invention may include program logic to determine when the selection control signal should indicate that the processor voltage signal should be selected by the multiplexer.
Another feature of the present invention may include program logic to determine when the selection control signal should indicate that one of the other voltage signals should be selected by the multiplexer.
In another embodiment, the method for biasing supply voltage requirements that are input to a voltage regulator includes:
inputting the processor voltage signal to the multiplexer, wherein the processor voltage signal is indicative of supply voltage required by one or more components in a computer system during operation;
inputting at least one other voltage signal indicative of supply voltage for a computer system to the multiplexer;
inputting a selection control signal to the multiplexer, wherein the selection control signal indicates a selection between the processor voltage signal and the at least one other voltage signal; and
outputting a voltage identification signal from the multiplexer to the voltage regulator, wherein the voltage identification signal is set to the processor voltage signal or the at least one other voltage signal, based on the selection control signal.
The present method may be used to test the computer system using supply voltages that are above or below specified operating voltages by setting one of the at least one other voltage signals to a desired value and inputting it as the voltage identification signal to the voltage regulator.
Alternatively, this method may be used to bias at least one of the other voltage signals to compensate the supply voltage to the voltage required by the computer system. This is useful when the supply voltage being provided by the voltage regulator is not within tolerance of the supply voltage required by the computer system.
One feature of the method includes determining when the selection control signal should indicate that the processor voltage signal should be selected by the multiplexer.
Another feature of the method includes determining when the selection control signal should indicate that one of the other voltage signals should be selected by the multiplexer.
Yet another feature of the method includes determining the bias to add to the margin voltage signal.
Thus, the present invention advantageously provides an apparatus and method for driving the voltages applied to a computer system to marginal values to test whether the computer system meets desired specifications.
The present invention also advantageously provides an apparatus and method for compensating for errors in the supply voltage output by the voltage regulator.
The foregoing has outlined rather broadly the objects, features, and technical advantages of the present invention so that the detailed description of the invention that follows may be better understood.